What specific error does this skill solve?

It solves the Ruff F821 'undefined name' error which occurs when a linter flags a module used in a type hint that isn't imported at the top level because it's an optional dependency.

Does this pattern affect runtime performance?

No. The imports inside the TYPE_CHECKING block are only executed by static analysis tools and IDEs, meaning there is zero performance overhead at runtime.

Will my IDE still show autocompletion for these types?

Yes, modern IDEs like VS Code and PyCharm specifically look for the TYPE_CHECKING block to provide intellisense and type checking even if the package isn't currently installed in your environment.

Why is 'from __future__ import annotations' necessary?

This import enables PEP 563, which tells Python to treat all type hints as strings, preventing the interpreter from trying to evaluate them at runtime when the module might not be installed.

Python Optional Dependency Type Checker

Name: Python Optional Dependency Type Checker
Author: smith6jt-cop

bysmith6jt-cop

Developer Tools

Resolves Ruff F821 undefined name errors for optional Python dependencies using the TYPE_CHECKING pattern.

About

This skill provides a standardized implementation pattern for handling type hints with optional dependencies—such as Pandas, Dask, or CuPy—without requiring them at runtime. By leveraging 'from __future__ import annotations' and the 'typing.TYPE_CHECKING' flag, it allows developers to satisfy static analysis tools like Ruff and maintain IDE autocompletion while preventing runtime import errors in environments where specific libraries are not installed. This is essential for building flexible Python libraries and data science pipelines that support multiple execution backends.

Key Features

Standardizes the use of quoted string annotations for type safety
0 GitHub stars
Implements PEP 563 postponed evaluation of annotations
Configures conditional import blocks using TYPE_CHECKING
Eliminates Ruff F821 'undefined name' linter errors
Maintains full IDE autocompletion for optional modules

Use Cases

Developing libraries with optional feature sets like GPU support via CuPy
Improving type safety in data science codebases with conditional imports
Resolving linter failures in CI/CD pipelines for multi-dependency projects

About

Key Features

Standardizes the use of quoted string annotations for type safety
0 GitHub stars
Implements PEP 563 postponed evaluation of annotations
Configures conditional import blocks using TYPE_CHECKING
Eliminates Ruff F821 'undefined name' linter errors
Maintains full IDE autocompletion for optional modules

Use Cases

Developing libraries with optional feature sets like GPU support via CuPy
Improving type safety in data science codebases with conditional imports
Resolving linter failures in CI/CD pipelines for multi-dependency projects